British prime minister David Cameron said Friday it was hard to persuade Russian President Vladimir Putin of the Syrian regime\'s alleged use of chemical weapons.Cameron, at a news conference following the G20 Summit in St. Petersburg, said Putin requested more evidence that proved President Bashar Al-Assad\'s regime used chemical weapons against civilians.Britain and the US will provide Putin with these evidence, he added, but it would be hard to persuade Putin to change his position that Assad used these chemical weapons against civilians in Ghouta, outside Damascus, on August 21.US President Barack Obama had said he believed America should carry out a strike against the Assad regime because of the alleged use of chemical weapons, which he said crossed the red lines.Meanwhile, 10 countries to the G20 summit supported the US planned strike against Syria.Australia, Britain, Spain, Italy, Canada, South Korea, Saudi Arabia, Turkey, France and Japan, in a statement available here, supported the US military action against Syria in retaliation of the chemical weapons\' attack because it was a blatant violation of the international law.The countries, in their statement, cited by Itar-Tass news agency, strongly condemned the chemical weapons\' attack against Ghouta which killed hundreds of people, and held the Assad regime responsible for the assault. They said the lack of reaction against this attack would encourage others to use chemical weapons in future.